1. Field of the Invention
The present invention relates to a method for making a perpendicular magnetic recording head which performs recording on recording media such as a disk having a hard layer by a perpendicular magnetic field. In particular, the present invention relates to a method for making a perpendicular magnetic recording head which suppresses fringing of a recorded pattern and is suitable for high-density recording.
2. Description of the Related Art
Perpendicular magnetic recording writes high-density magnetic data on a recording medium such as a disk. FIG. 32 is a cross-sectional view of a typical known perpendicular magnetic recording head H, which is used in apparatuses of a perpendicular magnetic recording type.
The perpendicular magnetic recording head H is provided at the trailing side 1a of a slider 1 which floats and moves on or slides on a recording medium Md. The perpendicular magnetic recording head H is disposed between a nonmagnetic layer 2 and a nonmagnetic coating layer 3 at the trailing side 1a. 
The perpendicular magnetic recording head H includes an auxiliary magnetic pole layer 4 composed of a ferromagnetic material and a main magnetic pole layer 5 composed of a ferromagnetic material on the auxiliary magnetic pole layer 4 with a gap provided therebetween. The end face 4a of the auxiliary magnetic pole layer 4 and the end face 5a of the main magnetic pole layer 5 are exposed at an opposing face Ha opposing the recording medium Md. The auxiliary magnetic pole layer 4 and the main magnetic pole layer 5 are magnetically coupled with each other at a magnetic coupling portion 6.
The auxiliary magnetic pole layer 4 and the main magnetic pole layer 5 are separated by a nonmagnetic insulating layer 7 composed of an inorganic material, for example, Al2O3 or SiO2. Thus, the end face 7a of the nonmagnetic insulating layer 7 is exposed between the end face 4a and the end face 5a at the opposing face Ha.
A coil layer 8 composed of a conductive material such as Cu is embedded in the nonmagnetic insulating layer 7.
The thickness hw at the end face 5a of the main magnetic pole layer 5 is smaller than the thickness hr at the end face 4a of the auxiliary magnetic pole layer 4. The width of the end face 5a of the main magnetic pole layer 5 in the X direction (track width direction) in the drawing defines the track width which is remarkably smaller than the width of the end face 4a of the auxiliary magnetic pole layer 4 in the track width direction.
The recording medium Md which is subjected to magnetic recording by the perpendicular magnetic recording head H moves in the Y direction relative to the perpendicular magnetic recording head H. The recording medium Md has a hard layer Ma at the surface and a soft layer Mb at the inner side.
When a recording magnetic field is induced in the auxiliary magnetic pole layer 4 and the main magnetic pole layer 5 by a current flowing in the coil layer 8, a leakage magnetic field between the end face 4a of the auxiliary magnetic pole layer 4 and the end face 5a of the main magnetic pole layer 5 perpendicularly permeates the hard layer Ma of the recording medium Md towards the soft layer Mb. Since the area of the 5a of the main magnetic pole layer 5 is remarkably smaller than the area of the end face 4a of the auxiliary magnetic pole layer 4, as described above, the magnetic flux Φ is concentrated to a region which opposes the end face 5a of the main magnetic pole layer 5 and performs recording on the hard layer Ma at this region.
FIG. 33 is a partial front view of the perpendicular magnetic recording head shown in FIG. 32, viewed from the opposing face to the recording medium. The main magnetic pole layer 5 of the perpendicular magnetic recording head is formed by plating a magnetic material on a magnetic underlayer 5b. The resulting main magnetic pole layer 5 has a convex upper surface 5c. Both sides 5d are perpendicular to the track width direction (X direction in the drawing).
FIG. 34 is a plan view of a recorded track on the recording medium in which a signal is recorded by the perpendicular magnetic recording head shown in FIGS. 32 and 33.
When the slider 1 moves between an outer track and an inner track on the disk recording medium Md, the sides 5d of the main magnetic pole layer 5 sometimes tilts from the direction (Z direction in FIG. 33) perpendicular to the recording medium Md to generate a skew angle. When the sides 5d of the main magnetic pole layer 5 are perpendicular to the track width direction as shown in FIG. 33, the skew angle of the sides 5d of the main magnetic pole layer 5 from the direction (Z direction in the drawing) perpendicular to the recording medium causes the sides 5d to generate an oblique fringing magnetic field F at the exterior of the track width Tw, as shown in a broken line, resulting in deterioration of off-track performance.
Furthermore, the convex upper surface 5c of the main magnetic pole layer 5 forms a convex magnetic domain boundary which spreads the pulse width of the waveform to be recorded. This phenomenon precludes the formation of a definite recorded magnetization distribution when higher-density recording is performed. Accordingly, the recording density in the direction along the recording track (A direction in FIG. 34) does not increase.